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Why your event photos band, and how Bandaid fixes it

Three short reads, from the physics of blinking LEDs to the signal processing that measures the stripes and divides them out. Each one has interactive figures, and the algorithm demos run the same code as the app.

Why LED banding happens PWM dimming, rolling shutters, why fast shutter speeds make it worse, and where magenta bands come from. Includes a shutter simulator. The physics · 8 min How Bandaid removes banding Line medians, spectral detection, lock-in demodulation and the full-resolution fix, with live demos of each step. The algorithm · 12 min FAQ Privacy, what it can and can't fix, reading the instrument panel, export options, and avoiding banding in camera. Quick answers

The 30-second version

  1. LEDs blink. They're dimmed by switching on and off hundreds or thousands of times a second. Your eye averages it out; a short exposure doesn't.
  2. Sensors scan. Each row of the sensor is exposed a moment after the row above, so different rows catch different parts of the blink. That gives bands.
  3. Bands are a per-row multiplier. Every pixel in a row is darkened by the same factor, separately for red, green and blue.
  4. Bandaid measures that multiplier. It takes medians across rows to ignore the scene, finds the steady band rhythm in the spectrum, and tracks it area by area, per colour.
  5. Then it divides it out at full resolution, lifting each row to match the clean bands. All of this happens in your browser.

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